Reproducer for phonographs



UNITED STATES i CHARLES G. HENSLEY, 0F vBROOKLYN,NEIN YORK.

REPRODUCER FOR PHONOGRAPI-IS.

Specification of Letters Patent.

Patented May 24, 1921.

lApplication filed May 20, 1916, Serial No. 98,723. Renewed October 4, 1919. Serial No. 328,608.

T 0 all whom t may concern.'

Be it known that I, CHARLES G. HENSLEY, a citizen of the United States, and a resident of the borough of Brooklyn, city and State of New York, have inventedcertain new and useful `Improvements in Reproducers for Phonographs, of which the following is a specification.

My invention relates to a reproducer or sound box for all forms of talking machines, including phonographs, graphophones and all machines wherein sound Waves are reproduced from a record. rThe reproducer, as is Well known in theart, is that part of the apparatus wherein the impressions or undulations on a record, tablet or cylinder, are translated into vibrations on a diaphragm, causing sound Waves, Which are conveyed from the reproducer to a horn or other amplifier. My invention relates tothe reproducer in which the vibrations of the diaphragm are translated into sound Waves and sent forth to be amplified.

Reproducers as heretofore made have been but partially successful as there are certain defects inherent in their construction and heretofore the efforts expended in perfecting the phonograph have been along the lines of improving the sounds after leaving the re' producer, rather than in removing the fundamental errors in the construction of the reproducer. While partial results have been attained I have found that it is impossible to rectify sound waves and to bring them back to their original quality by merely improving the amplifying means, where the Waves have been erroneously translated in and delivered from the reproducer.

The general and accepted construction of reproducers has consisted of a rear, flat wall of metal having a tubular outlet at its center and a diaphragm close to and parallel with the metal Wall, together with a pivoted stylus lever connected at one end to the center of the diaphragm. The sound Waves are created by movement of the diaphragm caused by the end of the stylus lever acting on the central point thereof. The diaphragm is flexed more or less according tothe extent of movement of the stylus lever from time to time, depending upon the intensity of the Waves being reproduced; but inevery case the movement is greatest at the center of the diaphragm and it decreases toward the edge, at the extremity there being no movement if the diaphragm is firmly clamped. In the present form of reproducer the tube from which the sounds are delivered s just opposite the central part of the diaphragm Where the movement is greatest, but Where even the most delicate sound Waves must originate. In F ig. 6 I have shown, diagrammatically, the present form of reproducer, in order that vthe same may be read in relation to this analysis of its defects.

I have found that the propagation of Sound Waves in an inclosure is in many Ways analogous to the flow of iiuids in an inclosure or conductor and that it is governed by Similar factors, though the principle 'of amplification, which is not related to the flow of fluids, modiesthe laws relating to the travel of sound Waves. rIhe same atom displaced at the centralv portion of the 'diaphragm may not pass through the tone arm and horn of a phonograph, nevertheless it is displaced to a certain extent depending upon the movement of the diaphragm; and the atom with which it impinges to propagate the sound is moved a certain extent; the" atoms, as it were, acting as runners in a relay, each traveling back and forth in some degree. These atoms traveling back and forth are affected by similar factors which affectthe flow of fluids, such as Water, through spaces. A tube or orifice Which Will cause greater velocity in a body of fluid passing through"than would some other tube of a different shape, will have a somewhat similar effect on the movement of sound Waves so long as the principle of amplification is not permitted to change the effect.

From the aboveI have reasoned that in order to get clear tones from a reproducer and to get the tones out of the phonograph to avoidthe muffled or inclosed effect it is desirable to employ a reproducer wherein the sound waves will be propagated with the greatest velocity and wherein the propagation will be effective for Waves of different quality or intensity. So far as I know no one has heretofore associated the thought of velocity of sound with the principles" of the flow of fluids and that is one of the reasons why the development of the phonograph has been on a sort of hit or miss plan.

In the ordinary reproducer no particular thought has been devoted to the question of l propagating with greatest velocity. In the ordinary reproducer the factors which would in the case of very delicate tones the move- Y.

ment may be limited to a` small space around the central point; but at this central point the air pressure is much different to what 1t is at the extremities of the diaphragm where the air is almost inclosed. The exit tube is opposite the central point of the diaphragm and therefore the velocity of sound waves created by a slight movement of the central portion of the diaphragm is disproportionate to waves created by a more extensive movement of the diaphragm.

Furthermore, as the sound waves are created at the center of.` the ordinary diaphragm, they tend to expand in sp erical form in accordance with well known laws of acoustics, but while part of the waves pass directly out through the tube in front of the diaphragm, some portion thereof expands out in the space between the diaphragm and its parallel opposing wall and this gives rise to many A"of the artificial and unnatural.' effects characteristic of the phonograph. For instance, the waves are held temporarily inl this space and lag behind those which pass directly into the tube. The waves which pass i-nto the lateral space are more or less confined since the casing is closed around the edge, and in order that tliese waves may pass out they must return l from the outer extremities of the space` to the central tube.

` terference.

I believe that these returning waves afectthe waves subsequently forming at the center of the diaphragm and giverise more or less -to theartificial and confusing sounds of the phonograph. I am aware that sound waves created at different points may cross each other more or less without interference, but I aminclined to believe that waves moving from the outer extremity of a" partial inclosure'toward the center while others are moving from the center toward the extremity, all the waves being concentric, cause in- Whether this be true or not it is certain that what I call the returning waves and which are not to be confused wit the rareication impulse as distinguished from the compression impulse of a complete sound wave, as they may consist of the rarefication or compression, reverberate between the metallic wall and the diaphragme- This tends to cause confusion of sound waves and to form false waves or to distort the natural waves.

These returning waves, or waves recrossing the diaphragm, by reverberating between the diaphragm. and metallic opposing wall are affected more or less by the metal in the wall, whether it be thick or thin and the tones are given a metallic quality, regardless of the material of which the diaphragm may be made. The reverberations between the diaphragm and opposing wall are more or less increased by reason of the fact that the opposing wall and diaphragm are generally parallel. Edison has attempted to mitigate the evil by making the opposing wall curved or like the interior of a cone, but then the wall acts like a focusing sound board and sends the waves outwardly instead of condensing them and sending them through the tube or tone arm. rl`his is one instance where the laws of the ampliiication and movement of sound diverges from or interferes with the laws affecting the yordinary movement of uids 'in spaces. There is asfmuch lost as gained by making the opposing wallconical instead of flat, without making other changes. On the other hand, it does not matter if the yopposingv wall is parallel with the diaphragm but it is rather an advantage, provided the sound waves do not recross the diaphragm as pointed out above.

It has not been practicable to make reproducers of wood heretofore,V notwithstanding the fact that mellow tones can best be produced with wood rather than metal, be-

cause this would introduce other difficul-` in suicient volume to be effective.

I have explained my theories regarding the defects in present practice in order to make clear the principles of my invention. Whether orl not these theories are partly or wholly wrong I nevertheless followed them 'in my' experiments andI have produced a device which overcomes previous A defects and which seems to verify the theories.

Some of the advantages .flowing from my invention are as follows:

As above Set forth, mellow, as distinguished from harsh, metallic tones,may be obtained. The enunciation is perfect or nearly so. The tones are sustained. Overtones or harmonics are obtained. Conflict in tones is lacking. A band piece. of any number of instruments, or a chorus 'of many voices may be reproduced without conflict of tones and one tone, voice or instrument, does not decrease or drown out another, as they are reproduced like the original rendition. 'lllie accompaniments are brought out to the proper degree. rThe tones get out of the phonograph better, eliminating thelmufhed effect. When the device is made of wood the needle scratch is reduced or made less oensive. Jall tones are more nearly like the original tones from which the records are made. Deep bass tones are reproduced which in the ordinary reproducer are entirely lost.

ln the drawings forming part of this application,

Figure 1 is a plan view of the reproducer,

Fig. 2 is an end elevation thereof, looking at the front or diaphragm end, these figures showing the device in a size suitable for actual practice,

Fig. 3 is a longitudinal sectional view, taken on the'line 3 3 of Fig. 1, showing the parts on an enlarged scale,

Fig. a is a cross sectional view taken on the line 4-t of Fig. 3,

Fig; 5 is an elevation of the inner or core member, and

Fig. 6 is a diagrammatic view of the form of reproducers heretofore used.

The reproducer comprises an outer member or shell 1 an `inner member or core 2, a

diaphragm 3 and a stylus lever 4. The lat-A ter may be of any shape or design and in the drawing l have shown a well known form of stylus lever.

The shell 1 has a rabbet 5 to receive the rubber gasket 6 which holds the diaphragm, and the outer rim of the latter sets in agroove in the gasket, so that when the gasket and diaphragm are placed in the rabbet 5 the diaphragm will extend across the open or larger end of the shell. rlhere is a. metal ring 7` which is forced into the rabbet to press upon the gasket 6 and hold the outer edge of the diaphragm firmly in place. Preferably, there is a flat metal ring 8 secured against the end of the shell by screws 9, the purpose of which is to hold the ring 7 from accidental displacement .and to protect the end of the shell from chipping, if the latter is made of wood.

The smaller end 10 of the shell is adapted to fit snugly over the end of the tone arm 11 of a phonograph and a screw 12 may be provided to fit into the bayonet joint 13 in the tone arm to secure the reproducer in position. I prefer to provide a metal cap 14 fitting over the rear or tube end of the shell to protect the latter."-

:The stylus lever is shown'rocking upon fulcrum screws 15 secured in a mounting or bracket 16 which is set into a recess 17 in the shell and secured thereto by screws 18.

The stylus lever is shown provided with the usual stylus hole 19 and with a stylus holding screw 20. The stylus lever bends inwardly toward the diaphragm at 21 and then horizontally at 22.` The latter part is tapped to receive a screw 23 which passes through the diaphragm and secures the central part of the diaphragm and the stylus lever together. The form of stylus lever and the form of mounting and the means for attaching it to the diaphragm are shown herein by way of example and itl is to be understood that they may be modified the same as in any other reproducer.

The inner or core member is placed within the shell member and as one means of holding it in spaced relation to the shell l have shown equally spaced pins 24 projectl ing from the core member and lying against the inner surface of the shell. lnaddition, there are screws 25 passing through the shell and entering apertures 26 in the `core member. y ln the full embodiment of my invention the shell member, 1 and the inner or core member 2 are made of wood. Also the shell member is made with a thick wall in order that the soundV waves will not be amplified in the shell and lpass laterally out but will be caused to pass through the tone arm. lf the wall of the shell is made thin the tones escape at the reproducer and very little volume is delivered through the tone arm. The core member is preferably a solid body of wood so that it is less resonant.. lf it is hollow or resonant it acts somewhaty like a reiiector and sends the sound waves away from instead of through the tone arm. e

The core is of gradually decreasing diameter from its front end to the rear end formin a truncated cone, the smaller end 27 being cut on a plane at right angle to the axis.

The core is so positioned in the shell that sufficient space to permit of the flexing of the diaphragm in response to the movement of the stylus in following the waves of the record groove. The thinner the space 29 the better the sounds seem to get out, and they seem to be clearer. In order to have the core as close as possible to the diaphragm a recess 30 may be cut therein to allow for the free movement of the head of the screw 23.

The bore 31 of the shell 1 is tapering, and the core is so positioned that a space 32 is formed between the core and shell which space is annular in cross section and which is in the form of a hollow cone. The distance between the core andthe shell may` be comparatively small but the distance between them at 33 should not be greater than at the forward end of the core, such as at 34, as otherwise the volume of sound delivered from the phonograph will be materially less. The distance between the core and shell at 33 may be even slightly less than at 34. The interioi` of the shell is preferably .curved at 35 to allow a somewhat freer space where the waves pass around the front edge of the core member.

'Ihe best results may be obtained when the smaller end of the core terminates a short distance within the tapering bore 3l of the shell as shown in the drawings.

W'hen the device is in operation and the stylus is' following the record groove, the stylus lever operates to Hex .the diaphragm at its center, moving it varying extents and y at varying rates of speed, according to the character of the sound waves to be reproduced. The waves thus created pass outwardly from the space 29 and through the tapering space 32 to the tone arm. Each sound wave passes directly out through the Apassages best adapted to its delivery in .full

volume through the tone arm, and aglven sound wave does not have to recross the diaphragm as in other reproducers. llsound waves are treated alike, so that the various phragm, but the same defects which occur in other reproducers having a wallparallel with the diaphragm, are not present in this opposed to the diaphragm'throughout thev construction. The waves are created primarily at the center of the diaphragm and pass of the outer portion thereof, 'without' having to return across the diaphragm in order to get out. The diaphragm may be exed without undue hindrance and it can set up the intermediate waves which cause the harmonics of the tones being reproduced. Itis a noticeable advantage of the present device that the true harmonics of the tones are reproduced. In the ordinary reproducer where some of the waves must recross the diaphragm in order to pass out through the tone arm, they set up false vibrations in the diaphragm and blank out or prevent `the formation of overtones or harmonics.

By having the front surface of the core greater part thereof and especially at the center, the most delicate sound waves are reproduced. This is noticeable in the more perfect rendition of the most delicate accompaniments, even while other and more intense sounds are being reproduced.

I have found that by making the reproducer of wood and in the manner shown herein, that mellow tones may be reproduced and with sutlicient volume. The tones are just as mellow as if the diaphragm itself were madepf wood. But sounds recorded by purely metallic instruments such as bells, are nevertheless accurately reproduced, as well as sounds which Vwere recorded by instruments made of wood, or by the human voice. Deep sounds, such as are made by bass instruments in a band or orchestra, are accurately reproduced with their overtones, whereas, in the ordinary reproducer, they either fail to reproduce or theirtones are so altered as to be quite differentto the original rendition.

I have found that the character of wood of which the reproducer is made has more or less effect upon the quality of the sounds. I have obtained excellent results with a reproducer made of clear pine and I believe that woods which are best suited for making musical instruments are likewise best adapted for the present reproducer. I have described in detail the proportions and arrangement of one embodiment of my linvention in order to teach the application thereof to practice, but I do not wish to be understood as limiting my invention to such proportions and details, but to include all devices which come within the spirit and scope of the annexed claims.' v

Having described my invention, what I claim is: 1. In a device for reproducing sound, a shell havinganoutlet, a diaphragm for creating sound waves in the shell and a solid member of wood l`in the shell and spaced therefrom, whereby waves produced by'said diaphragm will travel around said wooden member and between the latter and said shell and through said outlet.

2. In a device for reproducing sound, a shell made of wood, and having an outlet, ay diaphragm for creating sound waves in the shell anda solid member of wood in the shell and spaced therefrom, whereby waves produced by said diaphragm will travel aroundsaid inner member and between the latter and said shell and pass through the outlet.

3. In a device for reproducing sounds, a wooden shell, a diaphragm for creating sound waves therein and an inner wooden member in said shell and spaced therefrom and from the diaphragm, wherebyY all waves created by the diaphragm will pass outwardly in the space between the diaphragm and said inner member and pass from the outer portion of the diaphragm between said shell and said inner member.

the shell and having its larger end arrangedI 4. In a device for reproducing sound, a shell, having an air chamber defined by a tapering surface, a diaphragm for creating sound waves in said chamber, and an inner member in said chamber spaced therefrom to form an air space between said shell and said inner member, the outer surface of said inner member being parallel with the inner surface of said shell fora substantiallportion of the length of said inner member, said inner member having a face opposed to and spaced from said diaphragm whereby all waves created in the shell by said diaphragm will pass outwardly ,in the space between said diaphragm and said inner member to the outer portion of the diaphragm and then pass around said inner member'.

5. In a device for reproducing sound, a shell of wood, a diaphragm for creating sound waves therein, and an inner member of wood so shaped and arranged in said shell and spaced therefrom to form a space in the form of a hollow cone, said inner member having a face opposed to and spaced from said diaphragm, whereby all waves created by said diaphragm will pass outwardly in the space between said diaphragm and said inner member to the outer part of the diaphragm and then pass through said space of hollow cone shape.

6. In a device for reproducing sound, a shell of wood and having a conically shaped `interior chamber, a diaphragm, an inner member of wood of conical shape, arranged in said chamber and spaced from said shell, said inner member being solid and having a substantially flat face close to and parallel with the diaphragm.

7. In a device for reproducing sound, a shell of wood, having a 'conically shapedinterior chamber, a diaphragm, an inner member of wood and of frusto conical shape, arranged in said chamber in spaced relation toy close to and parallel with the diaphragm.

8. In a device for reproducing sound, a

shell having a conically shaped interior chamber and an outlet, a diaphragm across relation to said shell to form a tapering space of annular cross section, the smaller end of said inner member terminating ahead of the smaller end of said conical chamber.

9. In a device for reproducing sound, a'

shell having an outlet and a tapering chamber leading thereto, a diaphragm across the larger end of said chamber, an inner member having a constant taper, arranged with its larger end opposed to and spaced from the diaphragm, said inner member being equally spaced from the inner surface of said shell and for a substantial portion of the length of the inner membeigto provide a `tapering space of annular cross section.

10. In a device for reproducing sound, a shell of wood having a thick wall and having a tapering inner chamber, an inner member of wood andof tapering shape, arranged in spaced relation to said shell whereby a tapering space of annular cross section is formed between said shell and said inner member, and a diaphragm acrossthe larger end of saidchamber and arranged close to the larger end of said inner member to form a sound space extending across the travel around said inner member and between the latter and said shell and through said outlet.

Signed at the city, county and State of New York, this 19th day of' May, 1916.

CHARLES G. HENSLEY. 

